FXUS66 KLOX 291218
AFDLOX
SOUTHWEST CALIFORNIA AREA FORECAST DISCUSSION
NATIONAL WEATHER SERVICE LOS ANGELES/OXNARD CA
420 AM PST SUN NOV 29 2009
NEW AVIATION DISCUSSION
.SYNOPSIS...
COOL TEMPERATURES AND OFFSHORE BREEZES WILL AFFECT THE AREA TODAY
AS A COLD LOW PRESSURE SYSTEM MOVES SOUTHEAST OUT OF THE AREA. THE
OFFSHORE BREEZES WILL CONTINUE INTO TUESDAY...BRINGING SEASONABLE
CONDITIONS TO THE AREA. WEAK ONSHORE WINDS WILL DEVELOP BY WEDNESDAY
RESULTING IN A SLIGHT COOLING TREND.
&&
.SHORT TERM (TODAY-TUE)...LATEST SATELLITE SHOWS COLD UPPER LOW
MOVING SLOWLY SOUTHWARD OVER THE FAR SOUTHEASTERN DESERTS. THE
NORTHEAST FLOW AROUND THIS SYSTEM IS PRODUCING SOME LIGHT SHOWERS
ACROSS INTERIOR SECTIONS OF LOS ANGELES COUNTY...BUT PER THE RAIN
GAGES...PRECIP AMOUNTS ARE QUITE LIGHT. SNOW LEVELS ARE CURRENTLY
AROUND 4000-4500 FEET. WITH THE SHOWER ACTIVITY EXPECTED TO CONTINUE
TO DIMINISH EARLY THIS MORNING...WILL LET THE WINTER WEATHER ADVISORY
EXPIRE AT 400 AM.
WITH THE PRECIP COMING TO AN END...THE MAIN FORECAST FOCUS IS ON
THE OFFSHORE WINDS. SURFACE HIGH PRESSURE WILL BUILD INTO THE GREAT
BASIN TODAY...SETTING THE STAGE FOR A WEAK TO MODERATE SANTA ANA
WIND EVENT. UPPER SUPPORT FOR THIS EVENT IS DECENT...WITH 25-40 KTS
OF SUPPORT THIS MORNING...AND 15-35 KTS ON MONDAY MORNING. PER
MODELS...THE STRONGEST OFFSHORE GRADIENTS WILL OCCUR ON MONDAY
MORNING. OVERALL...THIS LOOKS LIKE AN ADVISORY LEVEL EVENT FOR
VTU/LAX COUNTIES THROUGH MONDAY. CURRENTLY...WIND ADVISORIES ARE IN
EFFECT UNTIL NOON TODAY (AT WHICH TIME THE OFFSHORE WINDS SHOULD
WEAKEN SOMEWHAT). GIVEN THE GRADIENTS AND UPPER SUPPORT...THE WINDS
WILL LIKELY INCREASE TO ADVISORY LEVELS AGAIN TONIGHT...SO THE
WIND ADVISORIES MAY HAVE TO BE EXTENDED INTO MONDAY. BY MONDAY
NIGHT AND TUESDAY...THE OFFSHORE FLOW WEAKENS NOTICEABLY.
AS FOR TEMPS...TODAY WILL BE A COOL DAY...DESPITE THE OFFSHORE FLOW.
WITH THE CONTINUED OFFSHORE WINDS...MONDAY SHOULD WARM UP TO A FEW
DEGREES ABOVE SEASONAL (ESPECIALLY WEST OF THE MOUNTAINS). ON
TUESDAY...EXPECT SOME COOLING AS A WEAK ONSHORE FLOW ESTABLISHES
IN THE AFTERNOON.
.LONG TERM (WED-SAT)...FOR THE EXTENDED...FORECAST CONFIDENCE IS
LOW TO MODERATE AS THE GFS AND ECMWF DIFFER NOTICEABLY. THE GFS
KEEPS AN UPPER LEVEL RIDGE ALONG THE WEST COAST THROUGH THURSDAY
THEN DEVELOPS AN UPPER LEVEL LOW OVER NORTHERN CALIFORNIA ON
FRIDAY/SATURDAY. ON THE OTHER HAND...THE ECMWF DROPS AN INSIDE
SLIDER INTO THE GREAT BASIN ON WEDNESDAY/THURSDAY THEN BUILDS
AN UPPER LEVEL ALONG THE WEST COAST ON FRIDAY/SATURDAY.
GIVEN THESE VASTLY DIFFERENT SCENARIOS...DID NOT INTRODUCE MUCH
OF A NOTICEABLE CHANGE IN THE EXTENDED FORECAST...INDICATING
DRY AND NEAR SEASONABLE CONDITIONS.
&&
.AVIATION...29/1220Z.
CLEAR SKIES HOWEVER WINDY CONDITIONS EXPECTED WITH LOW LEVEL WIND
SHEAR AT KBUR AND KVNY.
KLAX...GOOD CONFIDENCE IN VFR CONDITIONS THROUGH SUNDAY NIGHT.
KBUR...GOOD CONFIDENCE IN VFR CONDITIONS THROUGH SUNDAY NIGHT. LOW
LEVEL WIND SHEAR AT TIMES.
&&
.LOX WATCHES/WARNINGS/ADVISORIES...
WIND ADVISORY (SEE LAXNPWLOX).
SMALL CRAFT ADVISORY FOR HAZARDOUS SEAS (SEE LAXMWWLOX).
HIGH SURF ADVISORY (SEE LAXCFWLOX).
HIGH RIP CURRENT RISK (SEE LAXSRFLOX).
&&
$$
PUBLIC...THOMPSON
AVIATION...SWEET
SYNOPSIS...RAT
WWW.WEATHER.GOV/LOSANGELES
